Process of extracting volatilizable metals from ores and metallurgical products



Nov. 19, 1929. PAPE 1,736,665-

PROCESS OF EXTRACTING VOLATILIZABLE [ETA LS FROI ORES AND METALLURGICAL PRODUCTS Filed April 19. 1927 Plas a! Nov. 19,1929

I WARN PAIE, OI OKEB/HARZ,

GERMANY, AS SIGNOB '10 FRIED. KBUPI GRUSON-e WEEK AKTIEN'GESELLSCHAFT, 01 MAGDEIBURG-IBUOKAU, GERMANY PROCESS OI nx'raacrme VOLATILIZABLE METALS FROM OBES AND METALLURGICAL PRODUCTS 7 Application filed April 18, 1927, Serial Io. 184,994, and in Germany April, 1928.

My invention relates to metallurgical processes pertaining'to the extraction of volatiliz able metals or metal compounds in the form of fumes or vapours from ores, and metal- I lurgical products of various kinds, containing said volatilizable metals as e. g. zinc, tin, lead, arsenic, bismuth, antimony, mercury etc. Metallurgical processes for the purpose under consideration commonly comprise com- 10 minuting the material to be treated and injecting or blowing it ina pulverulent form, mixed with fuel whenever required by the nature of the raw material, into a stationary metallurgical furnace,'so as to obtainia reduction and volatilization of the metals and also a combustion of any sulphur which may be contained in the material.

A serious'drawback connected with this procedure consists therein that the ulve'rulent material is not held long enoug in suspension in the furnace viz not long enough exposed to and in contact .with the flame with regard to the time required for the volatilization, and that a high proportion of the material will, before all the metal is volatilized, drop down rather quick to the bottom of the furnace where it mixes with'and is embedded in the slags and other molten residues thus being withdrawn from the attack of the m flame, and being lost in the discharged slags. Great efforts have been made to overcome .tsaid drawback by comminutin .the material to the highest possible grade 0 fineness, and also by increasing the temperature within the furnace; but the small percentage of metal recoverable in that way will not ustify in practice the expenses entailed thereby.

The object of my invention is to provide an improved process for the extraction of volatilizable metals which can be carried out in practice with greater economy than was possible heretofore, and which will yield bet ter results in regard to the total percentage of metal recoverable from the raw material under treatment.

The nature and scope of my invention are briefly outlined in the a pended claims, and will be more fully understood from the following specification taken together with the accompanying drawing'in which vverulent form into a rotary metallurgical furnace so as to heat the material, and to extract the volatilizable metals in the form of fumes and vapours whereby the particles dropping down to the bottom of the heating chamber are agitated and continuously discharged out of the furnace.

In passing through the furnace the material can be agitated and subjected to a subse uent volatilizing action.

y this mode of working it is to be attained that the non-volatilized components of the char e-gangue and metals or compounds of 7 meta swhich are deposited sooner or later according to their degree of fineness on the 4 bottom of the chamber, give up a part of their heat owing to the rotary movement to the mantle ofthe drum and are not subjected to smelting or that the parts which have already become liquid coagulate again before they can agglomerate to lumps of larger size. It may of advantage to withdraw in the a known manner heat out of the mantle of the chamber apart from the natural cooling (loss of heat by radiation) by artificial cooling (air, water etc.) or to avoid an agglom eration of residues by adding stiffening material at the upper end of the chamber.

' In this way it is possible to subject the material which drops out from the flamecone proper before the-intended reaction is finished on the bottom of the rotating drum to a su sequent treatment by radiation of heat, treatment with air or in a given case also by means of reducing or oxidizing materials. The heat resulting from the burning of the reaction products and of the fuel introduced serves. to maintain the reacgaseous fuel mixed with the material or infurnace and are carried out of the furnace therewith due to the inclined position and rotation of the furnace; Any additional material for reducing purposes that may have to be added in order to obtain a reducing effect should be blown, either at the upper end of the drum or by a special feeding appliance into the material whereby the rotary movement of the chamber causes automatically an intimate mixture with the mate rial. Owin to the inclined osition of the bottom of t e rotating cham er'continuous forward movement in the kiln and a discharge of the residuesis attained. Further more one is able to adjust the speed of the gases and the time they remain in the kiln in conformity with the local condition by means of the diameter and the length of the kiln, and to obtain thereby agood separation between the solid product of reaction and the metal fumes, oxides etc. which may have to be led away.

' When treating sulphurous materials it is possible to combine a very thorough expulsion of the sulphur with the volatilization.

Fig. 1 shows a tubular rotary furnace for carrying out the above outlined process in practice: The comminuted material is injected or blown through a nozzle (1 by injecting means known. per se in the artinto the rotating combustion chamber 71 of the furnace at its lower end 6 The furnace is heated'by a flame which may be convenient 1y produced by burning pulverulent or troduced separately, and by supplying reducing agents in a solid or gaseous state.

The gaseous products of combustion containing volatilized "metals in the form of fumes or vapors are dischargedthrough the flue d at the upper end I) of the combustion chamber.

0 The material 0 which drops out of the flame onto the inner wall of the combustion chamher will travel alon its inclined bottom in counter current to t e gaseous roducts of combustion so as to be discharged at f.

In the rotary furnace shown by way of an example in Fig. 2 my process is carried out in a slightly modifled form: The comminuted material is injected or blown through nozzle 0 into the upper end-b of the combustion chamber 6 As in the case of Fig. 1 the furnace is heated by a flame which may be conveniently produced by burning pulverulent or gaseous fuel mixed with the material or introduced separately, and by supplying reducing agents in a solid or aseou's state. The gaseous products of com ustion containingvolatilized metals in the form of fumes or vapours'are discharged through the flue d at the lower end 6 of the furnace. The material 0 which drops out of the flame onto the inner wall of the combustion chamber 6 will travel therethrough in the same direction as the gaseous products of combustion, and is discharged at F.

Stifi'ening agents may be introduced e. g. through a chute e. I In passing through the furnace the material can be agitated and subjected to a subsequent Very effective Volatilizing action by the flame which may be conveniently still enhanced by mixing the material also with oxidizing or reducing agents consistent with its respective nature and composition.

Various changes and modifications may be made in the design and the structural details of rotary furnaces used consistent with the nature of the material to be treated, and in possible results by my improved process without substantially departing from the spirit of this invention.

Thus e. g. the rotary furnace may be given a conical shape having a sloping surface at its bottom such as is shown, for example, in U. S. Patent No. 959,924 to Dedolph.

The process of this invention may be applied to the treatment of a zinc ore as follows A poor ore containing about 10% zinc is pulverized to particles of about 1 mm. size andis injected in admixture with carbon into a rotating oven by means of compressed air. The amount of air used is in excess of that necessary for the combustion of the carbon. First the carbon is burned locally in the up-. per portions of the oven to CO and this reducing gasreduces a part of the zinc oxide contained in the ore. The zinc volatilizes at the prevailing tem erature but is again immediatel converte into zinc oxide, due to the oxi izing atmosphere which is maintained within the oven, is carried off as oxide along with the oven gases, and is precipitated in a suitable apparatus. fall to the bottom 'of the oven due to their weight, where they'become' mixed with carbonwhich is char ed through the upper end of the oven, and dis mixture slowly travels toward the exit end of the bven in an uninterrupted thin stream due to the inclined position of the oven. Due to the burning of the zinc vapor and the complete combustionof the carbon dust which is injected along with the fine ore, a temperature is maintained throughout the greater part of the oven which heats the ore particles on the bottom of the The ore particles oven sufliciently so that under the influence of the added reducing agents the reduction and volatilization of the zinc is completed. The zinc free residue is discharged from the oven at its lower end.

What I claim is: 1. Process of recovering volatilizable metals from ores, metallurgical products and v the like, which comprises injecting the material to be treated in a finely divided and suspended state into a rotating metallurgical furnace in which an oxidizing atmosphere is maintained, introducing fuel into the furnace, heating the injected material while it is still in a suspended state and volatilizing metal therefrom by burning the fuel, and volatilizing furtherquantities of metal from the residues which settle to the bottom of the furnace under conditions avoiding slagging or fusion of these. residues.

2. Process of recovering volatilizable metals from ores, metallurgical products and the like, which comprises injecting fuel in admixture with the material to be treated in a finely divided and suspended state into a retating metallurgical furnace in which an oxidizing atmosphere is maintained, burning the fuel whereby the material undergoin treatment isv heated and metal volatilize; them from'while the said material is still in the suspended state, mixing fuel with the residues which settle to the bottom of the fur- 1 nace, and volatilizing further quantities ofmetal therefrom under conditions avoiding slagging or fusion of these residues.

The foregoing specification signed at Berlin this 5th day of A ril, 1927.

RMANN PAPE. 

